scaleway-functions-go

README

Scaleway Functions Go

Library authored By Scaleway's Serverless Team.

This repository contains a runtime wrapper necessary to develop with Golang on Scaleway Functions (Scaleway's Function As A Service Product). It allows users to deploy Golang Function Handlers in the cloud by adding the transport/event formatting layer on top of the developer's codebase.

Basically, this project will stand as the Function's Gateway, starting an HTTP server to handle incoming traffic by transforming requests in Golang Event Structures and execute handlers defined by the developer with these structures.

Disclaimer: This library is heavily inspired by aws lambda go as we target compatibility with AWS Lambda Code (Allow users to develop for lambda and deploy on Scaleway Functions with minimal changes in their codebase). This way, you may already be familiar with API Gateway Event, Context and Response structures.

Scaleway Functions Go is intended to be used by developers, who want to use Golang runtime to run FAAS Applications on Scaleway Functions.

Requirements

In order to use this project, you will need:

• Golang
• Package manager for go such as dep.

Install

In order to start development on your Serverless Application with Go, you have to install this project as a dependency, for example with dep:

dep ensure -add github.com/scaleway/scaleway-functions-go

Please Note that you will have to package your vendors when uploading your codebase to Scaleway Functions, as we will take care of building your code. This is why we use dep in this example.

Getting Started

In order to run a Function in the cloud, you must specify a handler function in your code, which will execute your business logic.

Here is some sample code to run a basic function on Scaleway Functions.

You may take a look at this directory for other examples.

package main

import (
	"encoding/json"

	"github.com/scaleway/scaleway-functions-go/events"
	"github.com/scaleway/scaleway-functions-go/lambda"
)

func handler(req events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
	response := map[string]interface{}{
		"message": "We're all good",
	}

	responseB, err := json.Marshal(response)
	if err != nil {
		return events.APIGatewayProxyResponse{}, err
	}

	return events.APIGatewayProxyResponse{
		Body:       string(responseB),
		StatusCode: 200,
	}, nil
}

func main() {
	lambda.Start(handler)
}

There are multiple important things to note inside above code snippet:

• package main is required (so we can execute the main function inside your package).
• import both scaleway-functions-go/events and scaleway-functions-go/lambda (library developed inside this repository).
• a handler function is defined, with events.APIGatewayProxyRequest as a parameter (contains informations about HTTP event triggered), and must return an APIGatewayProxyResponse structure, and an error.
• a main function, calling lambda.Start with the handler, described by the developer.

All the wrapping logic is contained inside lambda.Start and makes sure your code runs properly on our platform. As we will execute your main package, this main function will be executed to bootstrap the environment when a function instance is triggered.

Please Note that a function instance will be created when an event is triggered, but will stay up for a little bit of time. Thus, the same function instance may be executed for multiple events. This way, you may configure some initialization logic (for example, opening a connection to a Database), outside of the main function so it only gets executed once at startup. Here is an example starting up a connection to a MySQL Database:

package main

import (
	"fmt"
	"os"
	"log"
	"database/sql"
	_ "github.com/go-sql-driver/mysql"
	"github.com/scaleway/scaleway-functions-go/events"
	"github.com/scaleway/scaleway-functions-go/lambda"
)

// global instance of database
var db *sql.DB

// Initialization logic, executed at function startup
func init() {
	var err error

	// Get Database configuration from environment variables
	dbName := os.Getenv("DB_NAME")
	dbUser := os.Getenv("DB_USER")
	dbPassword := os.Getenv("DB_PASSWORD")
	dbHost := os.Getenv("DB_HOST")
	dbPort := os.Getenv("DB_PORT")

	connectionString := fmt.Sprintf("%s:%s@%s:%s/%s", dbUser, dbPassword, dbHost, dbPort, dbName)
	db, err = sql.Open("mysql", connectionString)
	if err != nil {
		log.Fatalf("error received while opening connection to Database: %v", err)
	}
}

func handler(req events.APIGatewayProxyRequest) (events.APIGatewayProxyResponse, error) {
	// Do something with db instance
	//...

	return events.APIGatewayProxyResponse{
		Body:       "How to initialize stuff in a Scaleway Function",
		StatusCode: 200,
	}, nil
}

func main() {
	lambda.Start(handler)
}

Documentation and Useful links

• Product Information
• Official Scaleway Serverless Functions Documentation
• Official Scaleway Serverless Functions Developers Documentation
• Code examples

Contributing

This plugin is mainly developed and maintained by Scaleway Serverless Team but you are free to open issues or discuss with us on our Community Slack Channels #serverless-containers and #serverless-functions.

License

This project is MIT licensed.